It is known that in electric household appliances of the aforesaid type, a number of operating parameters should be known in order to ensure correct operation thereof, such as for example the uniformity degree of distribution of the laundry in the basket, the pressure and/or amount of feeding water, etc.
French patent application FR-A-2767194 describes a system for detecting some of these parameters using a pressure switch (pressure transducer) connected to the water feeding system of the electric household appliance and integrally coupled to a fluid-tight tank containing the rotating basket of the electric household appliance (washing or drying machine); as known, the tank is connected to the carcass of the electric household appliance, which supports it, by means of elastic, possibly damped elements, whereby it is relatively movable with respect to the carcass, upon the load applied thereto by the basket containing, in use, the laundry to be washed or dried.
The pressure switch includes a rigid casing accommodating a deformable membrane sensitive to hydraulic pressure, a core made of ferromagnetic material and fastened to the membrane, and a winding fixed to the casing and operatively coupled to the core to form a variable inductance inductor. The movements of the membrane are opposed by a low-stiffness spring or a pair of opposed, low-stiffness springs, so that the vibrations to which the movable member of the electric household appliance is subjected in use are transmitted to the pressure switch and in particular to the membrane, the movement of which, at least during some steps of the operating cycle of the electric household appliance, does not depend only on the differential pressure acting on the membrane, but also on the movements induced on the membrane itself by the vibrations, thus generating an electric signal responsive in direction and amplitude of the vibration of the basket.
However, the described detecting system is not free from drawbacks; in fact, it may by relatively inaccurate because the contrast springs should be calibrated so as to allow the membrane to move due to the vibrations in addition to pressure. For the same reason, the pressure switch provided so as to be inserted in such a system is relatively large in size; finally, mounting the pressure switch to the movable member of the electric household appliance is quite difficult.